角码未在浏览器中正确显示

Question

<nav class = "navbar navbar-default">
    <div class="container-fluid">
        <div class="navbar-header">
            <a href = "#" class="navbar-brand">Recipe Book</a>
        </div>
        <div class="collapse navbar-collapse">
            <ul class="nav navbar-nav">
                <li><a href="#">Recipes</a></li>
                <li><a href="#">Shopping List</a></li>
            </ul>
            <ul class="nav navbar-nav navbar-right">
                <li class="dropdown">
                    <a href="#" class = "dropdown-toggle" role="button">Manage<span class = 'caret'></span></a>
                    <ul class = "dropdown-menu">
                        <li> <a href = "#">Save Data</a></li>
                        <li> <a href = "#">Fetch Data</a></li>
                    </ul>
                </li>
            </ul>
        </div>
    </div>
</nav>

输出仅显示“ Recipe Book”，其余数据未显示...我正在使用Angular 8，并且bootstrap.min.css已添加到angular.json文件中...